Abstract: In this study, the flood prevention design methods for underground space in Japan are explored by providing a historical background on waterlogging in underground spaces and flood control policies in Japan. Then, the causes of waterlogging accidents in underground spaces are analyzed, including water overflow at the opening of the underground space, ineffective drainage leading to water accumulation, and evacuation difficulties during rescue efforts. Through an examination of literature and engineering design documents, the authors conclude that a comprehensive underground space flood control and drainage design system proposed by Japan can resist flood disasters. This system includes measures to prevent open water inflow, optimize drainage and water storage design, and improve disaster response within building spaces. It is also found that the installation of various waterretaining measures at entrances, vents, sunken squares, lighting wells, and other openings can effectively waterproof from the "source". Additionally, appropriate waterretaining measures can be selected based on the water inflow time and degree of the opening. Furthermore, the construction of urban drainage systems and underground water storage facilities can prevent water accumulation in underground spaces. Favorable underground space design can also effectively avoid accidents caused by evacuation difficulties. To cope with the flood disasters caused by global climate change, the authors suggest forming a complete disaster prevention system from three aspects: source waterproofing, process control, and engineering application. This comprehensive approach can effectively improve the flood control and drainage capacity of underground spaces.

Key words: Japanese underground space, flood prevention design strategy, antiflooding measures for opening part, drainage and water storage design, disaster response of building space